problem with 0.78 on Mac

I ran the installer of 0.78 on my Mac (which has no previous installation of zimbra desktop). At the end of the installation process I fill out the form for my zimbra account. When I press 'Save Settings' for the first time it shows:

system failure: java.lang.NullPointerException

The second time and any next time I press 'Save Settings' it shows:

email address already exists: 86e41f67-8d7f-49e3-a0b1-ce3a663a8cc7

Then I press 'Cancel' and it seems that the account is present, but with status 'error'

In ~zimbra/zimbra/zdesktop/log/mailbox.log I can see that zimbra desktop is retrieving stuff (calendar items right now).